A new study published in Nature Mental Health has linked prenatal exposure to acetaminophen-one of the most commonly used over-the-counter pain relievers-to an increased risk of attention deficit/hyperactivity disorder (ADHD) in children.
Researchers found that mothers who had detectable levels of acetaminophen in their blood during pregnancy were more than three times as likely to have a child diagnosed with ADHD. The study followed 307 pregnant women from 2006 to 2011, tracking their children's development for up to 10 years. Among children whose mothers took acetaminophen while pregnant, 18% were later diagnosed with ADHD, compared to 9% among those whose mothers did not use the medication.
"This medication was also approved decades ago and may need reevaluation by the FDA," Dr. Sheela Sathyanarayana, a pediatrician at the University of Washington and the study's senior author, said in a statement. "Acetaminophen was never evaluated for fetal exposures in relation to long-term neurodevelopmental impacts."
The effects appeared to be more pronounced in female children, with researchers reporting that girls exposed to acetaminophen in utero were six times more likely to be diagnosed with ADHD. Among boys, the study found a "positive but nonsignificant association" between acetaminophen exposure and ADHD risk.
Acetaminophen, best known as the active ingredient in Tylenol, is widely used to treat fever, headaches, muscle aches, and pain during pregnancy. It is classified as a Category B drug by the U.S. Food and Drug Administration (FDA), meaning that it is generally considered safe for use during pregnancy. According to estimates, between 40% and 60% of pregnant women take acetaminophen at some point during pregnancy.
The findings add to a growing body of research examining the potential risks of acetaminophen exposure during pregnancy. While some studies have suggested a link between prenatal acetaminophen use and neurodevelopmental disorders, others have found no significant association.
In 2015, the FDA reviewed the existing research and stated that the data were "too limited to make any recommendations." However, the agency advised that pregnant women should consult their doctors before using any pain medication.
Brennan Baker, the study's lead author and a researcher at Seattle Children's Research Institute, noted that previous research relied on self-reported data, which may not have accurately reflected acetaminophen use. The current study is among the first to use direct blood plasma measurements to assess exposure, strengthening the findings.
"There is obviously more work that needs to be done in this area," Baker said. "And we need to continually update our guidance."
